Method of controllably conveying an object and an apparatus for conveying a web

ABSTRACT

The present invention relates to a method of controllably conveying an object. The method comprises the steps of determining an intended conveying of the object, dividing, on the basis of a predefined profile for a second section (G) of the conveying, the intended conveying of the object into a first section (F) and a second section (G), conveying the object the first section (F), conveying the object the second section (G), and, during the second section (G) of the conveying of the object, registering an actual position of a predefined element linked to the object. The present invention further relates to an apparatus for reducing this method into practice.

This application is a U.S. national stage application based onInternational Application No. PCT/SE2004/001203 filed on Aug. 17, 2004,and claims priority under 35 USC §119 to Sweden Application No.0302493-2 filed on Sep. 19, 2003, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of controllably conveying anobject or intermittently conveying objects during which conveying orindexing an actual position of a predefined element linked to the objectis registered.

The present invention further relates to an apparatus for processing aweb of packaging laminate, comprising at least one processing stationwhich is disposed to intermittently execute a processing operation onthe web, a drive unit which is disposed to convey the web passed theprocessing station, a control unit which is disposed to control theconveying by the drive unit of the web, and a sensor unit which isdisposed to register the position of a predefined element linked to theweb.

BACKGROUND OF THE INVENTION

It has long been known to produce food packages of different types frompackaging laminates. One commercially viable method is to continuouslyunite the longitudinal edges of a web and thereby form the web into atube which is thereafter filled and sealed and severed transversely ofthe longitudinal direction of the web so that a number of cushion-shapedindividual packages are formed. Depending upon the mutual orientation ofthe transverse seals and depending upon subsequent final folding, thesepackages may be given different configurations. Examples of suchconfigurations are the tetrahedral package which is marketed by TetraPak under the name Tetra Classic®. Another example of such a package isthe brick-shaped package which is marketed by Tetra Pak under the nameTetra Brik®. This generic type of package is well-known both to personsskilled in the art and consumers and will not be described in greaterdetail here. The brief description, given by way of introduction, of themethod of realising such packages is also well-known to a person skilledin the art and will not be described in greater detail either. Onlythose details of such a filling machine as are encompassed by theinventive concept as herein disclosed and an understanding thereof willbe described in greater detail.

During the last decade, it has become increasingly common practice toprovide, above all, the traditional, brick-shaped packages withdifferent types of opening arrangements. One type of opening arrangementis described in EP 949 992 A1. This opening arrangement is realised inthat a hole is punched through the packaging laminate, whereafter thishole is covered by an opening arrangement which is injection mouldedstraight over the hole. The injection moulding is put into effect inthat a moulding tool is placed on either side of the packaging laminateso that the mould cavity formed by the moulding tools completelyencloses the previously punched hole. By injecting hot, mouldableplastic into the entire mould cavity, the hole is sealed. This type ofopening arrangement is normally formed with a weaker portion whichextends about a greater part of the circumference of the openingarrangement so that a consumer may open the package by breaking a partof the opening arrangement along the weakening.

In order to realise such an opening arrangement, it is important to beable to place the hole punched in the web in the correct position in theinjection moulding station. EP 1 110 867 A1 describes how it is possibleto employ the hole as a reference point for positioning thereof in theinjection moulding station. The traditional method prior to this was toemploy some form of guide mark in order to position the packaginglaminate web both before the punching operation and then before theinjection moulding operation. One problem which may thereby occur isthat a sum total is made of two error tolerances so that the openingarrangement is not injection moulded over the hole within its mutualtolerances. By measuring the position of the hole for positioning beforethe injection moulding, this tolerance accumulation chain has beeneliminated.

EP 1 110 867 describes a set of three punches and three injectionmoulding stations where three mutually subsequent packaging blanks arepunched simultaneously and three mutually subsequent packaging blanksare provided with opening arrangements by injection mouldingsimultaneously.

Recently, there has been an increasing demand for small packages,so-called portion packages, for example of the order of magnitude of 150ml and upwards. One problem which has thereby occurred is that thedistance between the hole positions of two mutually adjacent packagingblanks will be so slight that it is difficult to construct injectionmoulding units which can be positioned so close to one another. EP 1 249399 describes how this problem has been solved by first punching, forexample, every second packaging blank and thereafter indexing one stepso that the other packaging blanks are punched. Once all packagingblanks which lie adjacent one another have been punched, a longerindexing is put into effect (for example five steps) so that all punchedpackaging blanks are conveyed past the punch units.

In connection with this type of indexing, with short and long indexsteps, it has nevertheless been possible to observe a difficulty inachieving an acceptable level of repeatability in the positioning. Aboveall, this problem has been observed at high machine speeds. The indexingprinciple described in EP 1 249 399 functions excellently, but forcertain machine construction and certain speeds the idea needs to befurther developed in order to be able to meet the requirements forcorrect positioning within very narrow positioning tolerances.

SUMMARY OF THE INVENTION

It is, thus, one object of the present invention to realise a method ofcontrollably conveying an object. A further object is to realise amethod which will be able to be employed in a large number of differenttypes of conveying and which, for these different types of conveyingwill nevertheless give consistent positioning.

These objects have been attained according to the present invention by amethod of controllably conveying an object or of intermittentlyconveying objects to a desired position, the method being characterisedby the steps of: determining an intended conveying or indexing distanceof an object; on the basis of a predefined profile for a second sectionof the indexing, dividing up the indexing of the object into a firstsection and a second section; conveying the object the first section;conveying the object the second section; and during the second sectionof the indexing of the object, registering an actual position of apredefined element linked to the object and adapting, on the basis ofthe registered actual position of the predefined element, the secondsection of the indexing of the object so that the intended conveying orindexing of the object is attained.

It is to be understood that the expression “profile” in relation to aconveying here refers to a speed profile for a “speed/time” or a“speed/distance” curve, as will be further explained below.

By predefining a special profile for the second section of the intendedconveying or indexing this may be adapted in order to give the mostdistinct and correct read-off, at the same time as the first section ofthe total conveying can be formed in the simplest, and thereby mostrapid possible manner. It has thus become possible to unite the twootherwise apparently contradictory objects of as rapid indexing orconveying as possible with as exact indexing or conveying as possible.Moreover, it has been possible to realise a solution to the problem ofhow to be able to realise different types or lengths of the differentindexing or conveying steps. By separating the second section and makingthis second section in compliance with a predefined profile, it will beensured that the second section of the conveying may be formed in thesame manner regardless of how long the total indexing is to be. Byforming the system and controlling it so that the position of thepredefined element (for example a hole in a packaging laminate web), isregistered during the second section of the indexing, for each type ofindexing (regardless of total length) the position will be registeredduring the same type of movement for all indexings. As a result, thismakes it largely possible to eliminate most types of dynamic effectswhich may otherwise affect the correct positioning. When a mechanicalsystem is to accelerate an object, this will imply that the mechanicalsystem will per se be flexed. In this case, the term flexed is taken tosignify, for example, stretching of belts, flank play in gears, elasticoutward flexing of frames, in other words all types of mutual movementthat can be generated in the system. Under a given acceleration, i.e. acertain force on the object, the mechanical system will undergo acertain flexing. Above all, there will be a considerable differencebetween an acceleration and a retardation, since all clearances or playin the system will instantaneously change direction. With the methodaccording to the present invention of controlling the conveying, it hasthus been ensured that all tolerance chains lie in the same mannerregardless of whether the conveying distance is short or long.

The above described control system and method can, in principle, beemployed for all types of conveying or indexing to a processing stationof any kind. The problems which were previously considered and thesolutions which are mentioned above are, however, substantially focusedon processing and indexing of a packaging laminate which forms arelatively flexible web which may readily be bent around a roller orbegin to undulate if the tensile stress in the web is too low. Forexample, it has proved to be advantageous if possible to read-off a holein a packaging laminate web during the acceleration phase of the web,since the web is then taut and displays a clearly defined length withoutany undefined undulations. By dividing up the indexing into a first andsecond section, it is possible to form the speed profile for the secondsection so that there is an acceleration phase where it is to beexpected to be able to read-off the position of the hole. Withtraditional indexing technology, it would be necessary in such an eventto make the read-off in the introductory phase of the indexing. However,this would introduce a new error source since, in long indexing, itwould entail a long conveying distance between read-off and finalposition which increases the risk that some mutual movement may takeplace, such as, for example, that a web slips in relation to a roller.

The above-described method may include methods where the conveying isarrested completely according to the first section before the secondsection is initiated, but in many cases it is to be preferred if it ispossible to realise the division of the first section and the secondsection while maintaining movement.

Preferred embodiments of the present invention are apparent from theappended subclaims.

According to one preferred embodiment, the method according to theinvention further includes the steps of adapting, on the basis of theregistered actual position of the predefined element, the second sectionof the conveying of the object so that the intended conveying of theobject is achieved. By such means, it is simply possible to adjust thespeed of the object or the web and the total conveying or indexing sothat, for example, the hole arrives at the correct position withoutneeding to adjust the position of the subsequent processing station.

Advantageously, the profile for the second section of the conveying ispredefined so that the position of the predefined element is registeredduring an acceleration phase of the profile of the second section of theconveying of the object. As was mentioned above, it is possible toensure that the read-off of the position takes place during a point intime when the web is reliably taut without any undefined undulationswhich would otherwise have a negative effect on the final positioning.

According to one preferred embodiment, the web consists of a packaginglaminate. As was mentioned above, the present invention is eminentlysuitable for indexing or conveying packaging laminate since this is arelatively flexible material. The term packaging laminate is taken tosignify various types of packaging materials which are intended to becut and folded together to form a package. One common example is apaper-based packaging laminate with inner and possibly also outer,liquid-tight coatings of a plastic material. Other examples are varioussingle-ply or multiply material of plastic or paper. It is also usualpractice to provide such packaging laminate with a barrier of, forexample, aluminium foil.

According to one preferred embodiment, the predefined element consistsof a hole formed through the web. As was mentioned above, the presentinvention is eminently suitable for indexing and conveying a web in amachine which is disposed to intermittently provide a packaging blankwith an opening arrangement which covers a hole in the web.

According to yet a further preferred embodiment, the method furthercomprises the steps of, on a first occasion, determining the intendedconveying of the object to a first distance and, on a second occasion,determining the intended conveying of the object to a second intendeddistance which is separate from the first distance, to divide, on thebasis of the same predefined profile, the first intended distance andthe second intended distance each into a set of first and secondsections of the conveying, the intended second section of eachrespective intended distance being equal and the first section of eachrespective intended distance being formed to be unequal in order toachieve different total intended distances. By such means, a method willbe obtained of catering for different lengths of the total indexing andnevertheless maintaining the desired predefined second section of theindexing. This method of controlling the apparatus is eminently suitablefor the system described by way of introduction comprising threemutually adjacent processing stations which are run at so-called 1:5indexing (i.e. 1 step and 5 steps alternately). The second sectionremains adapted for correct position registration, while the firstsection is formed so as to realise, in the quickest possible manner, theremaining portion of the total length of the conveying or the indexing.

Advantageously, the method is adapted to realise a first totalconveying, in that the object a) is accelerated and retarded or b) isaccelerated, run at substantially constant speed and retarded during thefirst section of the conveying before the second section of theconveying is initiated. By such means, it is possible to realise a rapidindexing of the first section and nevertheless achieve a state which isadapted in order that the second section will be able to be initiated ina uniform manner.

Preferably, the retardation in the first section of the conveyingcontinues until a predetermined position, predetermined time or apredetermined speed has been reached, whereafter the object is run at aconstant speed during a predetermined time or along a predeterminedtravel before the second section of the conveying is initiated. By suchmeans, it is possible to avoid the risk that dynamic effects from thefirst section of the indexing are propagated and affect the positioningin connection with the second section of the indexing. The choice as towhether to retard to a certain position, during a predetermined time orto a certain speed is largely determined by the relevant practicalapplication. If there is a large inherent inertia (and thereby greatkinetic energy) in the object which is being conveyed, it may, forexample, be advantageous to ensure that a correct speed is achieved,since even slight differences in speed give rise to major dynamicdifferences. In many cases, the use of position is desirable since it isthen possible to employ the intelligence inherent in most servo systems.If the servo system is provided with information as to the end position,the servo will, within predefined limit values of acceleration, maximumspeed and retardation, automatically displace the object to thisposition in the quickest possible manner. The choice of length of timeor distance and whether it is distance or time which is the essentialparameter for control during the constant movement before the secondsection of the indexing is determined to a great extent by the practicalfield of application in question.

Advantageously, the method is adapted so as to realise a second totalconveying in that the object is accelerated to a predetermined position,a predetermined time or a predetermined speed has been reached,whereafter the object is driven at constant speed during a predeterminedtime or along a predetermined distance before the second section of theconveying is initiated. By such means, it is simple to ensure that thesecond section of the indexing is realised in accordance with thepredefined profile even if the first section of the indexing inprinciple solely encompasses one initial acceleration. To repeat, it islargely the relevant practical application which determines theparameter which is most important to employ for the controlledtransition between the first and the second sections of the totalindexing.

The above-outlined objects have also been attained according to thepresent invention by means of an apparatus for processing a web ofpackaging laminate, comprising at least one processing station which isdisposed to intermittently execute a processing operation on the web, adrive unit which is disposed to convey the web past the processingstation, a control unit which is disposed to control the conveying bythe drive unit of the web in accordance with the method as set forth inany of appended claims 1 to 8, and a sensor unit which is disposed toregister the position of the predefined element linked to the web.

As was mentioned above, the described method is above all suitable foruse in an apparatus for applying opening arrangements on a packaginglaminate web. Also in that case where there is only one processingstation, the method according to the present invention is advantageousto employ, since it is possible to realise a read-off during a uniformacceleration phase which lies relatively close to the final positioning.Moreover, the system is, in such an event, adapted to be able to drivelonger indexings in those cases this is necessary. For example, it maybe necessary during an introductory phase to make longer indexings untilthe correct initial position has been arrived at.

Advantageously, the apparatus for realising an opening arrangement on apackaging laminate web comprises at least one hole making station whichis disposed to realise a through-going hole in the web and at least oneapplication station which is disposed to cover the hole with an openingarrangement. By such means, it is possible, as was mentioned previously,to provide a packaging laminate web with opening arrangements with thecorrect positioning.

Preferably, said at least one application station comprises at least oneinjection moulding station with moulding tools which are disposed toenclose between them in a mould cavity a portion of the web whichcomprises a hole formed in said at least one hole making station. As wasmentioned previously, this is an advantageous method of realisingopening arrangements which cover the hole formed in the packaginglaminate web.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detailhereinafter with reference to the accompanying schematic drawings whichshow, for purposes of exemplification, currently preferred embodimentsof the present invention.

FIG. 1 schematically illustrates the speed profile over the time for arelatively short conveying step;

FIG. 2 schematically illustrates the speed profile for a relatively longconveying step;

FIG. 3 schematically illustrates the speed profile according to priorart technology;

FIG. 4 schematically illustrates the speed profile for one relativelyshort conveying step and one relatively long conveying step;

FIG. 5 shows measurement data from a short indexing of one step followedby a long indexing of five steps; and

FIG. 6 schematically illustrates an apparatus for applying openingarrangements on a web of packaging laminate.

FIG. 7 schematically illustrates an alternative embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As is apparent from FIG. 6, the apparatus for applying openingarrangements on a web 1 comprises three punching stations 2 a-c andthree injection moulding stations 3 a-c. The web 1 is driven past thesestations over a number of rollers 4 a-d which may be driving, retardingor freely rotating. In order to be able to take up differences in webpositioning between the punching stations 2 a-c and the injectionmoulding stations 3 a-c, some of the rollers 4 b may also bedisplaceably journalled so that a loop of the web 1 may be made smalleror larger as needed. FIG. 6 shows one embodiment where the extent of theweb 1 through the injection moulding stations 3 a-c is substantiallydriven by the subsequent roller 4 d.

As was mentioned by way of introduction, the injection moulding stations3 a-c are described in greater detail in EP 949 992 A1. The threepunching stations 2 a-c may be of optional conventional type and willnot be described in greater detail here. Each one of the punchingstations is provided with a punch and an abutment on the other side ofthe web 1.

The apparatus is further provided with a sensor 5 which is disposed tobe able to read-off when a hole 9 punched in the web 1 in a punchingstation 2 a-c passes. The sensor 5 transmits a signal 6 to a controlunit 7. The control unit 7 transmits in turn a signal 8 to the drivingroller 4 d to control the web 1 so that the holes 9 read-off by thesensor 5 will arrive at the correct position in relation to theinjection moulding station 3 a-c. As was mentioned above, an apparatusof this type requires that special indexing sequences are introduced ifit is to be possible to make sufficiently small packages. This problemand different types of indexing sequences are described in detail in EP1 249 399 and will not, therefore, be described in greater detail inthis specification. Regardless of which indexing sequence is selected,the indexing- or conveying profile according to the present inventionmay be employed to improve the final positioning of the holes 9 in theinjection moulding stations 3 a-c.

FIG. 3 shows a traditional speed profile over the time for a relativelylong indexing. The web 1 if first driven in an acceleration phase inorder subsequently to change into a constant speed phase in orderfinally once again to be retarded to stationary. As will be apparentfrom FIG. 3, a hole 9 is read and gives a signal C which indicates thepassage of the first C1 and the second C2 hole edge. The first andsecond edges are detected and transmitted as a signal to a control unit.These signals are represented in FIG. 3 by two vertical lines C1, C2.

FIGS. 1 and 2 illustrate, in accordance with the present invention, twodifferent profiles which are intended for relatively short indexings andrelatively long indexings, respectively. Both of them have been realisedin terms of control engineering in the same manner. In this case, thetechnique will be described when the driving roller is a part of a servosystem with a certain inherent intelligence where the servo systemconstitutes a logical part of the control unit. First, the servo systemis provided with information that it is to run a certain distance S(possibly, a maximum acceleration, a maximum speed and a maximumretardation may also be defined). On the basis of this given distance S(see FIG. 4), the servo system will accelerate, drive further at aconstant speed and finally begin to brake (as shown in FIGS. 2 and 4).When it has almost arrived at the end, or as late as possible beforereaching S, it is given new information. In FIG. 1, this new body ofinformation is given already before it has reached maximum speed. InFIG. 2 and FIG. 4, this information is given just before it has stoppedagain. In FIG. 1, FIG. 2 and FIG. 4, the position for this point in timeis marked when a new information is given by reference numeral D. InFIG. 1 and FIG. 2 are shown examples where this point in time isdetermined by a certain speed A. Naturally, a given position or a givenpoint in time may also be employed. Employing a position isadvantageous, since most servo systems have integrated pulse counterswhich keep track of the position. Once this signal with information hasbeen given, the servo system is driven at constant speed for a briefperiod of time. This time is determined by how quickly it is necessaryto carry out the entire indexing and how quickly any possibleoscillations reduce in the system during constant operation. If use ismade of a position or a point in time for controlling the point for newinformation, it may be suitable to continue at the speed the web happensto be driven at at that point in time. As will be apparent from theforegoing description, a similar state has thus been arrived atregardless of whether a long or a short indexing has been driven.

After a given period of time (reference numeral E), the servo system isgiven new information as to an intended final position and within whichacceleration-, retardation- and speed limits the system may run. Theservo system will accelerate the web and the first C1 and second C2edges of the relevant hole 9 will be read-off. In FIG. 1, the relevanthole 9 is the first hole, while in FIG. 2, the relevant hole 9 is numberfive in the sequence. Which hole is read-off and how many which havebeen read before but not employed for controlling the positioningdepends, as was mentioned above, on what indexing principle is employed.The acceleration time or the acceleration distance has been selected sothat there is time to read both the first and the second edge during theacceleration. For example, it is possible to employ the last edgeread-off as a new point for controlling the servo system. When both ofthe edges have been read-off, it is possible to calculate the positionof the hole in relation to the expected stop position. Thereafter, newinformation is given to the servo system as to how the final positionindicated before the read-off is to be adjusted in order for the desiredfinal position to be achieved.

The long indexing will now be described in brief with reference to FIG.4.

1) Determine how far the indexing is to take place, i.e. the length of apackaging blank multiplied by the number of packaging blanks which areto be advanced past.

2) Determine whether this length makes it possible to have time to maketwo accelerations and retardations, i.e. if the intended indexing lengthis greater than the predefined profile.

3) Determine the first indexing distance S which is the total indexingminus the length of the predefined profile.

4) The first indexing distance S plus acceleration limit, retardationlimit and maximum speed are given to the servo system.

5) Immediately before the first indexing distance S has been completed,the signal is given that the servo is to run the total indexing distanceat maintained speed.

6) When a number of milliseconds have elapsed, a new signal is given tothe servo system. Run the total indexing distance and that accelerationand retardation are permitted within certain limits, and also thatmaximum permitted speed has been set at a higher level. In order toarrive there in the quickest manner, the servo system will thusaccelerate the web.

7) Read off the first hole edge and the second hole edge. Calculate anew value of end position. The new value of end position is given as thecentre of the hole (i.e. the position of the first hole edge plus theposition of the second hole edge and division of the total by two), plusa fixed distance which is geometrically determined by the distancebetween the sensor and the centre point in the injection mouldingstation.

8) Possibly, there may be an opportunity to adjust the last calculatedvalue using some form of operating panel in connection with the controlunit. This adjustment may be employed for finally adjusting thepositioning in relation to any possible incorrect mounting of thesensor.

FIG. 5 shows a measured speed profile for a one-step indexing withread-off of a hole followed by a five-step indexing with read-off offive holes where the first four holes are registered during the firstsection of the indexing and the last, in other words that hole which isemployed for adjusting the end position, is read-off during the lastsection of the indexing. In FIG. 5 it will be seen how the first sectionof the indexing takes place at high speed and that the second section ofthe indexing takes place with a profile which is the same as the profilewhich is employed during the last section of the one-step indexing. Boththe first and the second speed profiles are run in accordance with theabove-described composite profile. In the first profile, the firstsection has, however, only become an acceleration phase.

In an alternative embodiment, the invention can be used in a top fillingstation for packages. With reference to FIG. 7 a-c, a row of packages 21are controllably conveyed passed a filling station with three outlets 22for dispensing a product to one package each. In FIG. 7 a, package 1, 3and 5 are filled and than an conveying of the packages are executed adistance corresponding to one package, arriving at the positionillustrated in FIG. 7 b.

In the position of FIG. 7 b, the packages 2, 4 and 6 are filled and thana second conveying of the packages are executed a distance correspondingthis time to five packages, arriving at the position illustrated in FIG.7 c.

By providing means for detecting the inlet holes in or reference markson the packages (acting as predefined element linked to the package),the conveying of the packages can with advantage be performed using themethod according to the present invention. The intended two differentindexings or conveying distances are in this example corresponding toone and five packages and the respective distances are in turn dividedinto two sections. The second section of both distances being identicaland includes the reading of the actual position of a hole or referencemark to secure correct positioning of the package at the end of saiddistance. Hereby, irrespectively of the actual distance being one orfive packages, the second section G of each conveying distance always isthe same and always includes a reading of the actual position of a holeor reference mark to secure precision positioning of the conveyedpackage at the end of the indexing or intenden conveying.

For example:Conveying 1=1 package=F1+GConveying 2=5 packages=F2+Gwere G=½ package, F1=½ package and F2=4½ package

When starting Conveying 1, the first information given to a servo motorcomprises the distance of travel corresponding to ½ package which givesa profile for F1. Then the predefined profile for G is initiated and areading of actual position is performed during G and the predefinedprofile, if needed, is adjusted to secure the arrival in a correctposition.

When starting Conveying 2, the information given to the servo motorcomprises the distance of travel corresponding to 4½ package, whichgives the profile for F2. Thereafter the predefined profile for G isinitiated and a reading of actual position is performed during G and thepredefined profile, if needed, is adjusted to secure the arrival in acorrect position.

It will be readily perceived that numerous modifications of theembodiments of the present invention described herein are possiblewithout departing from the scope of the invention as this is defined inthe appended Claims.

For example, the sensor may be employed to read-off some otherpredefined element, such as a bar code or the like. Since the apparatusand the method according to the present invention make for narrowertolerance limits, it is possible to employ other read-off principleswhich in turn add different tolerances to one another.

In the specification, it is shown how different signals within thesystem are led via conductors, such as, for example, electrical oroptical conductors, but it is naturally possible to employ wirelesscommunications which, for example, utilise different types ofelectromagnetic waves.

Instead of adjusting the last part of the conveying of the web, it ispossible in certain cases instead to adjust the position of theinjection moulding stations once the passage of the holes has beenread-off and their expected stop position calculated. Above all, thiswould be of interest in those cases where there is a web or an object tobe conveyed which displays great inertia which may be adjustedpositionally only with difficulty.

1. A method of controllably conveying or intermittently conveying a webof packaging laminate provided with holes to at least one applicationstation which is disposed to cover said holes with opening arrangements,comprising the following sequential steps: determining a single intendedconveying or indexing distance of the web; on the basis of a predefinedprofile for a second section of the indexing, dividing up the singleintended indexing distance of the web into a first section and a secondsection; conveying the web the first section; conveying the web thesecond section; and during the second section of the indexing of theweb, registering an actual position of a pre-made hole in the web andadapting, on the basis of the registered actual position of the hole,the second section of the indexing of the web so that said hole arrivesat a correct position in relation to an application station for applyingan opening arrangement over said hole at a predetermined acceleration,thereby providing similar conditions each time an opening arrangement isapplied.
 2. The method as claimed in claim 1, further comprisingpredefining the profile of the second section of the indexing so thatthe position of the hole is registered during an acceleration phase ofthe profile of the second section of the indexing of the web.
 3. Themethod as claimed in claim 1, wherein the opening arrangement is appliedover said hole by injection moulding the opening arrangement withmoulding tools which are disposed to enclose between them in a mouldcavity a portion of the web which comprises the hole.
 4. The method asclaimed in claim 1, further comprising determining, on a first occasion,the intended conveying or indexing of the web to a first intendedindexing distance and, on a second occasion, determining the intendedconveying or indexing of the web to a second intended indexing distancewhich is separate from the first distance, dividing, on the basis of thesame predefined profile, the first intended indexing distance and thesecond intended indexing distance each into a set of first and secondsections of the indexing, the intended second section of each respectiveintended indexing distance being formed equally and the first section ofeach respective intended indexing distance being formed differently soas to achieve different total intended indexing distances.
 5. The methodas claimed in claim 1, wherein a first total indexing is realised sothat the web a) is accelerated and retarded or b) is accelerated, run atsubstantially constant speed and retarded, during the first section ofthe indexing before the second section of the indexing is commenced. 6.The method as claimed in claim 5, wherein the retardation in the firstsection of the indexing continues until a predetermined position, apredetermined time or a predetermined speed has been attained,whereafter the web is run at constant speed during a predetermined timeor along a predetermined distance before the second section of theindexing is commenced.
 7. The method as claimed in claim 1, wherein asecond total indexing is attained in that the web is accelerated until apredetermined position, a predetermined time or a predetermined speedhas been achieved, where after the web is driven at constant speedduring a predetermined time or along a predetermined distance before thesecond section of the indexing is commenced.